Automatic variable pitch propeller



I P 7, 1938. v. B. BRUM-WELL 2;1 3l, 2l7

AUTOMATIC VARIABLE PITCH PROPELLER Filed Dec. 12,1936

I Inventor A itorneys Patentedsept. 27 1938 UNITED STATES PATENT OFFICE.

s. 2,131,211 AUTOMATIC vaamam rrron rnoPELLEa Vincent Boyd Brnmwell, SanDiego, Calif. a Application Decemberlz, 1936, Serial No. 115,620

My invention relates 'generally to propellersan arrangement whichreducesthe strain on the' crankshaft and engine, and which permits the engineto turn at the samespeed at any altitude while the throttle is open.

Another important object of my invention is to provide a propeller ofthe character indicated in which there is practically no" pull whenlanding.

Other important objects of my invention will be apparent from a readingof the following description taken in connection with the drawing,wherein for purposes of illustration I have shown a preferred embodimentof my invention.

In the drawing:= Figure 1 is a general front elevational view of theembodiment.

Figure 2 is a front elevational view of one of the propeller blades.

Figure 3 is a horizontal sectional view taken through Figure 2approximately on the line 38 and looking downwardly in the direction ofthe arrow.

Figure 4 is a front elevational view. of the back section of the hub.Figure 5 is a side elevational view of the assembled hub sections. I

Figure 6 is a horizontal sectional view taken through Figure 4approximately on the line 66 and looking downwardly in the direction ofthe arrow.

Figure '7 is a top plan view of Figure 5. Referring in detail to thedrawing, the numeral 5 generally designatesthe hub of the propellerwhich is composed of the front section 6' and the rear section l.- Thesesections are substantially similar, each being provided with atransverse bore 8 with the requisite keyways! therein to receive thepropeller shaft. Each section 8, I is provided in its upper part with asemi-cylindrical chamber 10 and in its lower part below the bore 8 witha similar semi-cylindrical chamber II which isreversed with respect tothe chamber Ill, but longitudinally aligned therewith.

Around the outer wall of each of these chamhers is a land l2 which isdisposed at an'approximate 45 degree angle and which operativelycooperates with the correspondingly shaped and angulated grooves It inthe corresponding annulus It which is fastened to the arm or shaft ii ofthe corresponding propeller blade It. The 1 upper part of the annulus Ithas a reduced cylindrical portion I! which is received in andturns inthe reduced semi-cylindrical portion ll of the corresponding one of thechambers I0 and II, the shaft or arm l5 working through the receivl0 ingopening I9 in the top or bottom or end of the chamber. I

Each of the sections t and I is provided with a corresponding pluralityof registrable' bolt receiving holes 20 in which are disposed the 15bolts 2| to lock the sections together in registry as indicated inFigure 5 and in Figure 7.

' With the annuli ll of the respective propeller blades l6 mounted inthe chambers formed by'the registration of the chambers l0 and II, upon20 assembly of the sections 6 and I in the manner indicated, thepropeller is assembled for use and installation on the propeller shaft(not shown).

, The numeral 22 designates the trailing edge of the propeller blade l6,while the numeral 23 25 designates the leading edge of the propellerblade.

In this connection it is to be noted'that the trailing edge-isoil-center with respect to the leading edge, so that most of the windpressure will be on the trailing edge. 30

For a successful applicationlof the invention the propeller blade mustbe constructed so that are again equal. The 'blade also must beconstructed so that at every different engine speed the pitch of thepropeller must be at the most advantageous pitch. Thus in highaltitudeor 45 stratosphere flying where theair is thin, as'the higher altitudeis reached the wind pressure decreases gradually on the blades It. Thecentrif- Y ugal force increases slightly as the engine turns faster. Theblades are forced out further. Thus 50 the pitch increases until thewind pressure and centrifugal force are equal. This givesa maximumpropeller efliciency for stratosphere flying. As the plane gainsaltitude the pitch increases on the blades anddecreases when descending.when u landing the engine is idling and the pitch is back to zero or nopitch. Opposed blades are forced in opposite directions of rotation inimparting the pitch.

The grooves I3 and the lands l2 are arranged that when the propellerblades are in the pitch of zero or no pitch, and the hub is turnedfaster, the centrifugal force will force the blades to rotate outwardlyso as to increase the pitch of the blades as far as full speed and untilfull speed is reached. As the hub is slowed down, the pitch of theblades becomes automatically lessened until the zero pitch position isreached at idling speed of the engine. The greatest angle obtainable isabout 45 degrees or slightly more. As a higher altitude is reached in anaeroplane equipped with a propeller in accordance with the present in--vention, the centrifugal force will exceed the wind pressure on thetrailing edge of the blades, so that the blades will be forced to anincreased pitch whereat the wind pressure on the trailing edges of theblades will equalize the force of the centrifugal force.

Although I have shown and described herein a preferred embodiment of myinvention, it is to be definitely understood that I do not desire tolimit the application of the invention thereto, and any change orchanges may be made in the materials, and in the structure andarrangement of the parts, within the spirit, of the invention and thescopeof the subjoined claims.

What is claimed is:-

I. An automatic change pitch propeller of the class described comprisinga hub adapted for mounting on a propeller shaft, said hub havingradially extending portions each formed with a circular chamber and anopening in its outer end communicating with the chamber, propellerblades carried by said radialportions and each having a shaft partpassing through the opening and a circular part slidably located in thechamber, each blade having its trailing edge off-center with respect tothe leading edge to provide a greater wind pressure on the trailingsurface than on the leading surface, means in the chamber and means onthe circular portion for partly rotating e the blade when the same movesaxially, said circular portion having unimpeded sliding movement in thechamber aside from the frictional engagement of such means on thecircular portion with the means in the chamber, the parts being radiallyextending portions each provided with a chamber and each chamber havinga circular outer part and a circular inner part, the inner part being oflarger diameter than the outer part, an angularly disposed land on thecylindrical wall of the enlarged inner part of said chamber, propellersextendingjnto the radially extending portions of thehub and each havingon its inner end a circular portion of two diameters, the smallerportion having sliding movement in the smaller part of the chamber andthe larger part having sliding movement in the larger part of thechamher, said larger part having an inclined groove thereinfor'slidingly engaging the land, said circular portion having unimpededsliding movement in the chamber aside from the frictional engage ment ofthe land with the walls of the groove, each blade and its circularportion moving axially outwardly under the action of centrifugal forceof the rotating hub, each blade having its trailing edge oil-center withrespect to the leading edge to place the major portion of the bladesurface to the rear of the center of the blade, whereby the greater windpressure will be exerted on the traili'ng surface,.the parts beingconstructed and arranged to cause increased pitch of the blade when thesame is moved outwardly by centrifugal force and the pitch is decreasedby axially inward movement of the blade when the wind pressure on theblade exceeds the centrifugal force.

